Cable for transmitting high frequency electrical energy



C. S. FRANKLIN Dec. 5, 1933-.

CABLE FOR TRANSMITTING HIGH FREQUENCY ELECTRICAL ENERGY Filed Oct. 15, 1927 y w'm INVENTOR CHARLES SAMUEL FRANKLIN By 4 ATTORNEY Patented Dec. 5, 1933 UNITED s'rA CABLE FOR '1 res FREQUENCY ELECTRICAL ENERGY Charles Samuel Franklin, Buckhurst Hill, Essex,

England, asaignor to Radio Corporation of America, a corporation of Delaware Application October 15, 1921, Serial No. zzazar,

and m cm: mam October 19, 1926 11 Claims. (01.173-265) This invention relates to cables for transmitting high frequency electrical energy, and more particularly to cables such as those used for conveying energy at frequencies of the order of 12 x 10 cycles per second to or from a radio aerial for purposes of short wave radio telegraphv and telephony.

The primary object of this invention is to provide a transmission cable which will be extremely emcient at high frequencies.

Another object of the invention is to provide a cable simple in structure which will be durable and can be cheaply manufactured.

Other objects will become apparent from the specification when read with the accompanying drawing, in which,

Fig. 1 is a longitudinal sectional view of the preferred form of the invention, and

Fig. 2 is a sectional view taken on the'section A A of Fig. 1. i

In known arrangements for conveying energy at such high frequencies, parallel wires, ar-- ranged either in a metallic casing or left in the open, have been employed.

According to this invention a high frequency cable comprises an inner conductor located within an outer conductor and substantially air insulated therefrom. I

In the preferred form of the invention the outer conductor is earthed throughout.

The inner and outer conductors are arranged concentrically, and in the preferred form of the invention are formed as tubes or channels which may be of any desired section.

Referring to the drawing, the high frequency cable comprises two concentric tubular conductors 1 and 2. The outer conductor 2, is earthed throughout as indicated in the drawing. The inner conductor 1 is spaced from the outer conductor 2 by means of members 4 in the form of hard rubber or the like rings surrounding conductor 1 which members in turn carry mica, porcelain or glass insulating supports 3, located at different points in the length of the cable, and so formed and arranged that there is no cross section of the cable at which the space between the inner and outer conductors is wholly occupied by the insulating supports.

In this arrangement the inner conductor is substantially air insulated from the outer, and it will be seen' that the insulating supports 3 have a large leakage surface. I

I have found that the most eflicient transmission is obtained when the diameter of the outer conductor is substantially 3.7 times that of the inner conductor.

Having fully described and illustrated my invention I claim:

1. In radio apparatus for, conveying energy at high frequencies, an inner tubular conductor, in-

sulating members carried by said conductor, and spaced therefrom by means of a plurality of rings, and an outer tubular conductor retained in position relative to said inner conductor by said insulating members.

2. In radio apparatus for conveying energy at high frequencies, an inner tubular conductor,

mica insulating members carried by said conductor and spaced therefrom by means of a plurality of non-metallic rings, and a grounded outer tubular conductor retained in position relative to said inner conductor by said insulating members.

3. A high frequency transmission cable comprising an inner tubular conductor for conducting high frequency currents located within and substantially air insulated from an outer tubular conductor the diameter of which is substantially 3.7 times that of the inner conductor.

4. A high frequency transmission cable for emciently conducting high frequency currents comprising an inner conductor locatedwithin and substantially air insulated from an outer tubular conductor, said inner conductor retained concentrically within said outer conductor by a plurality of substantially tubular insulators having a plurality of central lobes, said insulators being spaced apart from said inner conductor by a pair of rings located at each end of said insulators.

5. A high frequency transmission line comprising inner and outer tubular conductors, a plurality of tubular insulators having a plurality of central external lobes, each of said. insulators cooperating with a pair of insulatedrings to retain said inner conductor concentric within said outer conductor.

6. A high frequency conductor for efficiently transmitting high frequency currents, comprising an inner and outer tubular conductor, a tubular insulator having a plurality of central external lobes, a pair of rings retained within each end of said insulators to concentrically space apart said inner conductor from the outer conductor.

7. A high frequency transmission cable comprising an outer and inner concentric tubular conductor, a plurality of insulators spaced at intervals between said conductors, each of said insulators having a plurality of central projections which touch the inner surface of said outer conductor, said projections being rounded at their point of contact with said outer conductor to provide a point of contact therewith, and spacing m'eans at the ends of said insulators to touch the outer-surface of said inner conductor.

8. A high frequency transmission cable comprising an outer tubular and inner cylindrical conductor, said conductors being arranged concentrically and being spaced from each other by ;plurality of outer contact points being arranged centrally on the outer surface of said insulator and the inner contact points of said insulator being longitudinally spaced and not in line with the outer central contact points.

9. A high frequency transmission cable comprising concentric tubular conductors, said conductors being spaced from each other at intervals by tubular insulators having a plurality of central spacing projections and a pair of rings located at each end of said insulators cooperating with the insulators to retain each of said conductors in concentric relationship.

10. In radio apparatus for conveying energy at high frequencies, a plurality of tubular conductors, one of which is grounded, and spaced. I

tubular insulating members interposed between said conductors for holding said conductors in spaced relation, said insulating members being of relatively small axial length and having a pluralityof central projections, said projections being rounded over at their point of contact to provide a substantial point contact with one of the conductors.

11. In radio apparatus for conveying energy at highfrequencies, an inner conductor and an outer conductor, insulating members of relatively small axial length having a plurality of central projections substantially rounded over at their point of contact with the outer conductor, said outer conductor surrounding said insulating members and the inner conductor which is retained concentrically in position with respect thereto and substantially air insulated therefrom by said insulating members.

CHARLES SAMUEL FRANKIJN. 

